The present invention relates to drills with drilling inserts and, more particularly, to drills with drilling inserts with chipbreaker arrangements.
In drilling operations, it is important to be able to remove chips formed from the workpiece from the hole being drilled in the workpiece. Removal of chips is facilitated when the chips are small so that they can be removed up the flutes of the drill. In drilling relatively ductile materials such as low carbon steel, and in drilling many of the stainless type steels and other alloys the chips tend to remain in relatively long lengths. During drilling operations, the more ductile that the material being drilled is, the longer the chips formed tend to be. It is therefore desirable to provide means for handling chips formed during a drilling operation, particularly for drilling in relatively ductile materials.
In accordance with an aspect of the present invention, a drill comprises a drill body comprising a shank end and a tip end, at least two flutes extending from the tip end toward the shank end, and an insert-receiving pocket disposed at the tip end of each flute, a peripheral one of the pockets being disposed closer to a radial periphery of the drill body than to a central axis of the drill body and a central one of the pockets being disposed closer to the central axis of the drill body than to the radial periphery of the drill body, a peripheral insert disposed in the peripheral pocket, the peripheral insert having a radial cutting edge extending generally in a direction of a radius of the drill body, a central insert disposed in the central pocket, the peripheral insert having a radial cutting edge extending generally in a direction of the radius of the drill body, wherein the peripheral insert comprises a rake face including a plurality of chipbreaker protrusions, and a first angle measured between a line tangent to forward ends of the plurality of chipbreaker protrusions and the central axis of the drill body extending toward the shank end is an acute angle.
In accordance with another aspect of the present invention, a peripheral insert for the defined drill comprises a rake face having a plurality of chipbreaker protrusions, wherein a first angle measured between a line tangent to forward ends of the plurality of chipbreaker protrusions defines a nonzero angle with an associated cutting edge of the peripheral insert.
The drill according to this aspect of the invention is particularly useful in evacuating chips formed during drilling operations in relatively ductile materials. More particularly, the structure of the drilling insert facilitates the formation of formed or rolled up chip that can be more easily removed through the flutes of the drill than long, straight chips. The configuration can decrease contact between the chip and the face of the drilling insert, can facilitate keeping temperature down as more tends to stay in the chip, reduce drilling forces, and extend tool life.